docs/apache-airflow/howto/notifications.rst

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Creating a notifier
===================
The :class:`~airflow.notifications.basenotifier.BaseNotifier` is an abstract class that provides a basic
structure for sending notifications in Airflow using the various ``on_*__callback``.
It is intended for providers to extend and customize for their specific needs.

To extend the BaseNotifier class, you will need to create a new class that inherits from it. In this new class,
you should override the ``notify`` method with your own implementation that sends the notification. The ``notify``
method takes in a single parameter, the Airflow context, which contains information about the current task and execution.

You can also set the ``template_fields`` attribute to specify which attributes should be rendered as templates.

Here's an example of how you can create a Notifier class:

.. code-block:: python

    from airflow.notifications.basenotifier import BaseNotifier
    from my_provider import send_message


    class MyNotifier(BaseNotifier):
        template_fields = ("message",)

        def __init__(self, message):
            self.message = message

        def notify(self, context):
            # Send notification here, below is an example
            title = f"Task {context['task_instance'].task_id} failed"
            send_message(title, self.message)

Using a notifier
----------------
Once you have a notifier implementation, you can use it in your ``DAG`` definition by passing it as an argument to
the ``on_*_callbacks``. For example, you can use it with ``on_success_callback`` or ``on_failure_callback`` to send
notifications based on the status of a task or a DAG run.

Here's an example of using the above notifier:

.. code-block:: python

    from datetime import datetime

    from airflow.models.dag import DAG
    from airflow.operators.bash import BashOperator

    from myprovider.notifier import MyNotifier

    with DAG(
        dag_id="example_notifier",
        start_date=datetime(2022, 1, 1),
        schedule_interval=None,
        on_success_callback=MyNotifier(message="Success!"),
        on_failure_callback=MyNotifier(message="Failure!"),
    ):
        task = BashOperator(
            task_id="example_task",
            bash_command="exit 1",
            on_success_callback=MyNotifier(message="Task Succeeded!"),
        )

For a list of community-managed notifiers, see
:doc:`apache-airflow-providers:core-extensions/notifications`.